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689ba89d | 1 | /* Perform doloop optimizations |
fa10beec RW |
2 | Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, |
3 | Inc. | |
689ba89d ZD |
4 | Based on code by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz) |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it under | |
9 | the terms of the GNU General Public License as published by the Free | |
9dcd6f09 | 10 | Software Foundation; either version 3, or (at your option) any later |
689ba89d ZD |
11 | version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
14 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
689ba89d ZD |
21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
26 | #include "rtl.h" | |
27 | #include "flags.h" | |
28 | #include "expr.h" | |
29 | #include "hard-reg-set.h" | |
30 | #include "basic-block.h" | |
31 | #include "toplev.h" | |
32 | #include "tm_p.h" | |
33 | #include "cfgloop.h" | |
34 | #include "output.h" | |
35 | #include "params.h" | |
a71a498d | 36 | #include "target.h" |
689ba89d ZD |
37 | |
38 | /* This module is used to modify loops with a determinable number of | |
39 | iterations to use special low-overhead looping instructions. | |
40 | ||
41 | It first validates whether the loop is well behaved and has a | |
42 | determinable number of iterations (either at compile or run-time). | |
43 | It then modifies the loop to use a low-overhead looping pattern as | |
44 | follows: | |
45 | ||
46 | 1. A pseudo register is allocated as the loop iteration counter. | |
47 | ||
48 | 2. The number of loop iterations is calculated and is stored | |
49 | in the loop counter. | |
50 | ||
51 | 3. At the end of the loop, the jump insn is replaced by the | |
52 | doloop_end pattern. The compare must remain because it might be | |
53 | used elsewhere. If the loop-variable or condition register are | |
54 | used elsewhere, they will be eliminated by flow. | |
55 | ||
56 | 4. An optional doloop_begin pattern is inserted at the top of the | |
57 | loop. | |
58 | ||
59 | TODO The optimization should only performed when either the biv used for exit | |
60 | condition is unused at all except for the exit test, or if we do not have to | |
61 | change its value, since otherwise we have to add a new induction variable, | |
62 | which usually will not pay up (unless the cost of the doloop pattern is | |
63 | somehow extremely lower than the cost of compare & jump, or unless the bct | |
64 | register cannot be used for anything else but doloop -- ??? detect these | |
65 | cases). */ | |
66 | ||
67 | #ifdef HAVE_doloop_end | |
68 | ||
69 | /* Return the loop termination condition for PATTERN or zero | |
70 | if it is not a decrement and branch jump insn. */ | |
71 | ||
75c70254 | 72 | rtx |
46dc0789 | 73 | doloop_condition_get (rtx doloop_pat) |
689ba89d ZD |
74 | { |
75 | rtx cmp; | |
76 | rtx inc; | |
77 | rtx reg; | |
75c70254 | 78 | rtx inc_src; |
689ba89d | 79 | rtx condition; |
46dc0789 | 80 | rtx pattern; |
689ba89d | 81 | |
46dc0789 MN |
82 | /* The canonical doloop pattern we expect has one of the following |
83 | forms: | |
689ba89d | 84 | |
46dc0789 MN |
85 | 1) (parallel [(set (pc) (if_then_else (condition) |
86 | (label_ref (label)) | |
87 | (pc))) | |
88 | (set (reg) (plus (reg) (const_int -1))) | |
89 | (additional clobbers and uses)]) | |
689ba89d | 90 | |
46dc0789 MN |
91 | The branch must be the first entry of the parallel (also required |
92 | by jump.c), and the second entry of the parallel must be a set of | |
93 | the loop counter register. Some targets (IA-64) wrap the set of | |
94 | the loop counter in an if_then_else too. | |
75c70254 | 95 | |
46dc0789 MN |
96 | 2) (set (reg) (plus (reg) (const_int -1)) |
97 | (set (pc) (if_then_else (reg != 0) | |
98 | (label_ref (label)) | |
99 | (pc))). */ | |
100 | ||
101 | pattern = PATTERN (doloop_pat); | |
689ba89d ZD |
102 | |
103 | if (GET_CODE (pattern) != PARALLEL) | |
46dc0789 MN |
104 | { |
105 | rtx cond; | |
106 | ||
107 | /* We expect the decrement to immediately precede the branch. */ | |
689ba89d | 108 | |
46dc0789 MN |
109 | if ((PREV_INSN (doloop_pat) == NULL_RTX) |
110 | || !INSN_P (PREV_INSN (doloop_pat))) | |
111 | return 0; | |
112 | ||
113 | cmp = pattern; | |
114 | inc = PATTERN (PREV_INSN (doloop_pat)); | |
115 | /* We expect the condition to be of the form (reg != 0) */ | |
116 | cond = XEXP (SET_SRC (cmp), 0); | |
117 | if (GET_CODE (cond) != NE || XEXP (cond, 1) != const0_rtx) | |
118 | return 0; | |
119 | ||
120 | } | |
121 | else | |
122 | { | |
123 | cmp = XVECEXP (pattern, 0, 0); | |
124 | inc = XVECEXP (pattern, 0, 1); | |
125 | } | |
689ba89d ZD |
126 | |
127 | /* Check for (set (reg) (something)). */ | |
75c70254 | 128 | if (GET_CODE (inc) != SET) |
689ba89d | 129 | return 0; |
689ba89d | 130 | reg = SET_DEST (inc); |
75c70254 SB |
131 | if (! REG_P (reg)) |
132 | return 0; | |
133 | ||
134 | /* Check if something = (plus (reg) (const_int -1)). | |
135 | On IA-64, this decrement is wrapped in an if_then_else. */ | |
136 | inc_src = SET_SRC (inc); | |
137 | if (GET_CODE (inc_src) == IF_THEN_ELSE) | |
138 | inc_src = XEXP (inc_src, 1); | |
139 | if (GET_CODE (inc_src) != PLUS | |
140 | || XEXP (inc_src, 0) != reg | |
141 | || XEXP (inc_src, 1) != constm1_rtx) | |
142 | return 0; | |
689ba89d ZD |
143 | |
144 | /* Check for (set (pc) (if_then_else (condition) | |
145 | (label_ref (label)) | |
146 | (pc))). */ | |
147 | if (GET_CODE (cmp) != SET | |
148 | || SET_DEST (cmp) != pc_rtx | |
149 | || GET_CODE (SET_SRC (cmp)) != IF_THEN_ELSE | |
150 | || GET_CODE (XEXP (SET_SRC (cmp), 1)) != LABEL_REF | |
151 | || XEXP (SET_SRC (cmp), 2) != pc_rtx) | |
152 | return 0; | |
153 | ||
154 | /* Extract loop termination condition. */ | |
155 | condition = XEXP (SET_SRC (cmp), 0); | |
156 | ||
75c70254 SB |
157 | /* We expect a GE or NE comparison with 0 or 1. */ |
158 | if ((GET_CODE (condition) != GE | |
159 | && GET_CODE (condition) != NE) | |
160 | || (XEXP (condition, 1) != const0_rtx | |
161 | && XEXP (condition, 1) != const1_rtx)) | |
689ba89d ZD |
162 | return 0; |
163 | ||
75c70254 SB |
164 | if ((XEXP (condition, 0) == reg) |
165 | || (GET_CODE (XEXP (condition, 0)) == PLUS | |
166 | && XEXP (XEXP (condition, 0), 0) == reg)) | |
46dc0789 MN |
167 | { |
168 | if (GET_CODE (pattern) != PARALLEL) | |
169 | /* The second form we expect: | |
170 | ||
171 | (set (reg) (plus (reg) (const_int -1)) | |
172 | (set (pc) (if_then_else (reg != 0) | |
173 | (label_ref (label)) | |
174 | (pc))). | |
175 | ||
176 | is equivalent to the following: | |
177 | ||
178 | (parallel [(set (pc) (if_then_else (reg != 1) | |
179 | (label_ref (label)) | |
180 | (pc))) | |
181 | (set (reg) (plus (reg) (const_int -1))) | |
182 | (additional clobbers and uses)]) | |
183 | ||
184 | So we return that form instead. | |
185 | */ | |
186 | condition = gen_rtx_fmt_ee (NE, VOIDmode, inc_src, const1_rtx); | |
187 | ||
689ba89d | 188 | return condition; |
46dc0789 | 189 | } |
689ba89d ZD |
190 | |
191 | /* ??? If a machine uses a funny comparison, we could return a | |
1ae58c30 | 192 | canonicalized form here. */ |
689ba89d ZD |
193 | |
194 | return 0; | |
195 | } | |
196 | ||
197 | /* Return nonzero if the loop specified by LOOP is suitable for | |
198 | the use of special low-overhead looping instructions. DESC | |
199 | describes the number of iterations of the loop. */ | |
200 | ||
201 | static bool | |
202 | doloop_valid_p (struct loop *loop, struct niter_desc *desc) | |
203 | { | |
204 | basic_block *body = get_loop_body (loop), bb; | |
205 | rtx insn; | |
206 | unsigned i; | |
7600f094 | 207 | bool result = true; |
689ba89d ZD |
208 | |
209 | /* Check for loops that may not terminate under special conditions. */ | |
210 | if (!desc->simple_p | |
211 | || desc->assumptions | |
212 | || desc->infinite) | |
213 | { | |
214 | /* There are some cases that would require a special attention. | |
215 | For example if the comparison is LEU and the comparison value | |
216 | is UINT_MAX then the loop will not terminate. Similarly, if the | |
217 | comparison code is GEU and the comparison value is 0, the | |
218 | loop will not terminate. | |
219 | ||
220 | If the absolute increment is not 1, the loop can be infinite | |
221 | even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2) | |
222 | ||
223 | ??? We could compute these conditions at run-time and have a | |
224 | additional jump around the loop to ensure an infinite loop. | |
225 | However, it is very unlikely that this is the intended | |
226 | behavior of the loop and checking for these rare boundary | |
227 | conditions would pessimize all other code. | |
228 | ||
229 | If the loop is executed only a few times an extra check to | |
230 | restart the loop could use up most of the benefits of using a | |
231 | count register loop. Note however, that normally, this | |
232 | restart branch would never execute, so it could be predicted | |
233 | well by the CPU. We should generate the pessimistic code by | |
234 | default, and have an option, e.g. -funsafe-loops that would | |
235 | enable count-register loops in this case. */ | |
236 | if (dump_file) | |
237 | fprintf (dump_file, "Doloop: Possible infinite iteration case.\n"); | |
7600f094 AP |
238 | result = false; |
239 | goto cleanup; | |
689ba89d ZD |
240 | } |
241 | ||
242 | for (i = 0; i < loop->num_nodes; i++) | |
243 | { | |
244 | bb = body[i]; | |
245 | ||
246 | for (insn = BB_HEAD (bb); | |
247 | insn != NEXT_INSN (BB_END (bb)); | |
248 | insn = NEXT_INSN (insn)) | |
249 | { | |
a71a498d AS |
250 | /* Different targets have different necessities for low-overhead |
251 | looping. Call the back end for each instruction within the loop | |
e7e64a25 AS |
252 | to let it decide whether the insn prohibits a low-overhead loop. |
253 | It will then return the cause for it to emit to the dump file. */ | |
254 | const char * invalid = targetm.invalid_within_doloop (insn); | |
255 | if (invalid) | |
256 | { | |
257 | if (dump_file) | |
258 | fprintf (dump_file, "Doloop: %s\n", invalid); | |
7600f094 AP |
259 | result = false; |
260 | goto cleanup; | |
e7e64a25 | 261 | } |
689ba89d ZD |
262 | } |
263 | } | |
7600f094 AP |
264 | result = true; |
265 | ||
266 | cleanup: | |
689ba89d ZD |
267 | free (body); |
268 | ||
7600f094 | 269 | return result; |
689ba89d ZD |
270 | } |
271 | ||
ed541ddb ZD |
272 | /* Adds test of COND jumping to DEST on edge *E and set *E to the new fallthru |
273 | edge. If the condition is always false, do not do anything. If it is always | |
274 | true, redirect E to DEST and return false. In all other cases, true is | |
275 | returned. */ | |
689ba89d | 276 | |
ed541ddb ZD |
277 | static bool |
278 | add_test (rtx cond, edge *e, basic_block dest) | |
689ba89d ZD |
279 | { |
280 | rtx seq, jump, label; | |
281 | enum machine_mode mode; | |
282 | rtx op0 = XEXP (cond, 0), op1 = XEXP (cond, 1); | |
283 | enum rtx_code code = GET_CODE (cond); | |
ed541ddb | 284 | basic_block bb; |
689ba89d ZD |
285 | |
286 | mode = GET_MODE (XEXP (cond, 0)); | |
287 | if (mode == VOIDmode) | |
288 | mode = GET_MODE (XEXP (cond, 1)); | |
289 | ||
290 | start_sequence (); | |
291 | op0 = force_operand (op0, NULL_RTX); | |
292 | op1 = force_operand (op1, NULL_RTX); | |
293 | label = block_label (dest); | |
294 | do_compare_rtx_and_jump (op0, op1, code, 0, mode, NULL_RTX, NULL_RTX, label); | |
295 | ||
296 | jump = get_last_insn (); | |
7d93d987 | 297 | if (!jump || !JUMP_P (jump)) |
f937df35 | 298 | { |
ed541ddb ZD |
299 | /* The condition is always false and the jump was optimized out. */ |
300 | end_sequence (); | |
301 | return true; | |
f937df35 | 302 | } |
689ba89d ZD |
303 | |
304 | seq = get_insns (); | |
305 | end_sequence (); | |
7d93d987 ZD |
306 | |
307 | /* There always is at least the jump insn in the sequence. */ | |
308 | gcc_assert (seq != NULL_RTX); | |
309 | ||
598ec7bd | 310 | bb = split_edge_and_insert (*e, seq); |
ed541ddb ZD |
311 | *e = single_succ_edge (bb); |
312 | ||
313 | if (any_uncondjump_p (jump)) | |
314 | { | |
315 | /* The condition is always true. */ | |
316 | delete_insn (jump); | |
317 | redirect_edge_and_branch_force (*e, dest); | |
318 | return false; | |
319 | } | |
320 | ||
321 | JUMP_LABEL (jump) = label; | |
322 | ||
323 | /* The jump is supposed to handle an unlikely special case. */ | |
324 | REG_NOTES (jump) | |
325 | = gen_rtx_EXPR_LIST (REG_BR_PROB, | |
326 | const0_rtx, REG_NOTES (jump)); | |
327 | LABEL_NUSES (label)++; | |
328 | ||
329 | make_edge (bb, dest, (*e)->flags & ~EDGE_FALLTHRU); | |
330 | return true; | |
689ba89d ZD |
331 | } |
332 | ||
333 | /* Modify the loop to use the low-overhead looping insn where LOOP | |
334 | describes the loop, DESC describes the number of iterations of the | |
335 | loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the | |
336 | end of the loop. CONDITION is the condition separated from the | |
a82bbcbb | 337 | DOLOOP_SEQ. COUNT is the number of iterations of the LOOP. */ |
689ba89d ZD |
338 | |
339 | static void | |
340 | doloop_modify (struct loop *loop, struct niter_desc *desc, | |
a82bbcbb | 341 | rtx doloop_seq, rtx condition, rtx count) |
689ba89d ZD |
342 | { |
343 | rtx counter_reg; | |
a82bbcbb | 344 | rtx tmp, noloop = NULL_RTX; |
689ba89d ZD |
345 | rtx sequence; |
346 | rtx jump_insn; | |
347 | rtx jump_label; | |
ed541ddb | 348 | int nonneg = 0; |
689ba89d ZD |
349 | bool increment_count; |
350 | basic_block loop_end = desc->out_edge->src; | |
a82bbcbb | 351 | enum machine_mode mode; |
80663107 | 352 | rtx true_prob_val; |
689ba89d ZD |
353 | |
354 | jump_insn = BB_END (loop_end); | |
355 | ||
356 | if (dump_file) | |
357 | { | |
358 | fprintf (dump_file, "Doloop: Inserting doloop pattern ("); | |
359 | if (desc->const_iter) | |
360 | fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC, desc->niter); | |
361 | else | |
362 | fputs ("runtime", dump_file); | |
363 | fputs (" iterations).\n", dump_file); | |
364 | } | |
365 | ||
fa10beec | 366 | /* Get the probability of the original branch. If it exists we would |
80663107 MN |
367 | need to update REG_BR_PROB of the new jump_insn. */ |
368 | true_prob_val = find_reg_note (jump_insn, REG_BR_PROB, NULL_RTX); | |
369 | ||
689ba89d ZD |
370 | /* Discard original jump to continue loop. The original compare |
371 | result may still be live, so it cannot be discarded explicitly. */ | |
372 | delete_insn (jump_insn); | |
373 | ||
374 | counter_reg = XEXP (condition, 0); | |
375 | if (GET_CODE (counter_reg) == PLUS) | |
376 | counter_reg = XEXP (counter_reg, 0); | |
a82bbcbb | 377 | mode = GET_MODE (counter_reg); |
689ba89d | 378 | |
689ba89d ZD |
379 | increment_count = false; |
380 | switch (GET_CODE (condition)) | |
381 | { | |
382 | case NE: | |
383 | /* Currently only NE tests against zero and one are supported. */ | |
b5e624c6 NS |
384 | noloop = XEXP (condition, 1); |
385 | if (noloop != const0_rtx) | |
689ba89d | 386 | { |
b5e624c6 | 387 | gcc_assert (noloop == const1_rtx); |
689ba89d | 388 | increment_count = true; |
689ba89d | 389 | } |
689ba89d ZD |
390 | break; |
391 | ||
392 | case GE: | |
393 | /* Currently only GE tests against zero are supported. */ | |
b5e624c6 | 394 | gcc_assert (XEXP (condition, 1) == const0_rtx); |
689ba89d ZD |
395 | |
396 | noloop = constm1_rtx; | |
397 | ||
398 | /* The iteration count does not need incrementing for a GE test. */ | |
399 | increment_count = false; | |
400 | ||
401 | /* Determine if the iteration counter will be non-negative. | |
402 | Note that the maximum value loaded is iterations_max - 1. */ | |
403 | if (desc->niter_max | |
404 | <= ((unsigned HOST_WIDEST_INT) 1 | |
a82bbcbb | 405 | << (GET_MODE_BITSIZE (mode) - 1))) |
689ba89d ZD |
406 | nonneg = 1; |
407 | break; | |
408 | ||
1c43d3ca | 409 | /* Abort if an invalid doloop pattern has been generated. */ |
8127d0e0 | 410 | default: |
b5e624c6 | 411 | gcc_unreachable (); |
689ba89d ZD |
412 | } |
413 | ||
414 | if (increment_count) | |
a82bbcbb | 415 | count = simplify_gen_binary (PLUS, mode, count, const1_rtx); |
689ba89d ZD |
416 | |
417 | /* Insert initialization of the count register into the loop header. */ | |
418 | start_sequence (); | |
419 | tmp = force_operand (count, counter_reg); | |
420 | convert_move (counter_reg, tmp, 1); | |
421 | sequence = get_insns (); | |
422 | end_sequence (); | |
423 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
424 | ||
425 | if (desc->noloop_assumptions) | |
426 | { | |
30d3fc60 | 427 | rtx ass = copy_rtx (desc->noloop_assumptions); |
689ba89d ZD |
428 | basic_block preheader = loop_preheader_edge (loop)->src; |
429 | basic_block set_zero | |
598ec7bd | 430 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 431 | basic_block new_preheader |
598ec7bd | 432 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 433 | edge te; |
689ba89d ZD |
434 | |
435 | /* Expand the condition testing the assumptions and if it does not pass, | |
436 | reset the count register to 0. */ | |
ed541ddb | 437 | redirect_edge_and_branch_force (single_succ_edge (preheader), new_preheader); |
689ba89d ZD |
438 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, preheader); |
439 | ||
440 | set_zero->count = 0; | |
441 | set_zero->frequency = 0; | |
442 | ||
ed541ddb ZD |
443 | te = single_succ_edge (preheader); |
444 | for (; ass; ass = XEXP (ass, 1)) | |
445 | if (!add_test (XEXP (ass, 0), &te, set_zero)) | |
446 | break; | |
447 | ||
448 | if (ass) | |
689ba89d | 449 | { |
ed541ddb ZD |
450 | /* We reached a condition that is always true. This is very hard to |
451 | reproduce (such a loop does not roll, and thus it would most | |
452 | likely get optimized out by some of the preceding optimizations). | |
453 | In fact, I do not have any testcase for it. However, it would | |
454 | also be very hard to show that it is impossible, so we must | |
455 | handle this case. */ | |
456 | set_zero->count = preheader->count; | |
457 | set_zero->frequency = preheader->frequency; | |
689ba89d | 458 | } |
ed541ddb ZD |
459 | |
460 | if (EDGE_COUNT (set_zero->preds) == 0) | |
461 | { | |
462 | /* All the conditions were simplified to false, remove the | |
463 | unreachable set_zero block. */ | |
ed541ddb ZD |
464 | delete_basic_block (set_zero); |
465 | } | |
466 | else | |
467 | { | |
468 | /* Reset the counter to zero in the set_zero block. */ | |
469 | start_sequence (); | |
470 | convert_move (counter_reg, noloop, 0); | |
471 | sequence = get_insns (); | |
472 | end_sequence (); | |
473 | emit_insn_after (sequence, BB_END (set_zero)); | |
474 | ||
475 | set_immediate_dominator (CDI_DOMINATORS, set_zero, | |
66f97d31 ZD |
476 | recompute_dominator (CDI_DOMINATORS, |
477 | set_zero)); | |
ed541ddb ZD |
478 | } |
479 | ||
480 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, | |
66f97d31 ZD |
481 | recompute_dominator (CDI_DOMINATORS, |
482 | new_preheader)); | |
689ba89d ZD |
483 | } |
484 | ||
485 | /* Some targets (eg, C4x) need to initialize special looping | |
486 | registers. */ | |
487 | #ifdef HAVE_doloop_begin | |
488 | { | |
489 | rtx init; | |
490 | unsigned level = get_loop_level (loop) + 1; | |
491 | init = gen_doloop_begin (counter_reg, | |
492 | desc->const_iter ? desc->niter_expr : const0_rtx, | |
1984d2e8 | 493 | GEN_INT (desc->niter_max), |
689ba89d ZD |
494 | GEN_INT (level)); |
495 | if (init) | |
496 | { | |
497 | start_sequence (); | |
498 | emit_insn (init); | |
499 | sequence = get_insns (); | |
500 | end_sequence (); | |
501 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
502 | } | |
503 | } | |
504 | #endif | |
505 | ||
506 | /* Insert the new low-overhead looping insn. */ | |
507 | emit_jump_insn_after (doloop_seq, BB_END (loop_end)); | |
508 | jump_insn = BB_END (loop_end); | |
509 | jump_label = block_label (desc->in_edge->dest); | |
510 | JUMP_LABEL (jump_insn) = jump_label; | |
511 | LABEL_NUSES (jump_label)++; | |
512 | ||
513 | /* Ensure the right fallthru edge is marked, for case we have reversed | |
514 | the condition. */ | |
515 | desc->in_edge->flags &= ~EDGE_FALLTHRU; | |
516 | desc->out_edge->flags |= EDGE_FALLTHRU; | |
517 | ||
518 | /* Add a REG_NONNEG note if the actual or estimated maximum number | |
519 | of iterations is non-negative. */ | |
520 | if (nonneg) | |
521 | { | |
522 | REG_NOTES (jump_insn) | |
523 | = gen_rtx_EXPR_LIST (REG_NONNEG, NULL_RTX, REG_NOTES (jump_insn)); | |
524 | } | |
80663107 MN |
525 | /* Update the REG_BR_PROB note. */ |
526 | if (true_prob_val) | |
527 | { | |
528 | /* Seems safer to use the branch probability. */ | |
529 | REG_NOTES (jump_insn) = | |
530 | gen_rtx_EXPR_LIST (REG_BR_PROB, | |
531 | GEN_INT (desc->in_edge->probability), | |
532 | REG_NOTES (jump_insn)); | |
533 | } | |
689ba89d ZD |
534 | } |
535 | ||
536 | /* Process loop described by LOOP validating that the loop is suitable for | |
537 | conversion to use a low overhead looping instruction, replacing the jump | |
538 | insn where suitable. Returns true if the loop was successfully | |
539 | modified. */ | |
540 | ||
541 | static bool | |
542 | doloop_optimize (struct loop *loop) | |
543 | { | |
544 | enum machine_mode mode; | |
545 | rtx doloop_seq, doloop_pat, doloop_reg; | |
a82bbcbb | 546 | rtx iterations, count; |
689ba89d ZD |
547 | rtx iterations_max; |
548 | rtx start_label; | |
549 | rtx condition; | |
7607bdda AT |
550 | unsigned level, est_niter; |
551 | int max_cost; | |
689ba89d | 552 | struct niter_desc *desc; |
a82bbcbb ZD |
553 | unsigned word_mode_size; |
554 | unsigned HOST_WIDE_INT word_mode_max; | |
689ba89d ZD |
555 | |
556 | if (dump_file) | |
557 | fprintf (dump_file, "Doloop: Processing loop %d.\n", loop->num); | |
558 | ||
559 | iv_analysis_loop_init (loop); | |
560 | ||
561 | /* Find the simple exit of a LOOP. */ | |
562 | desc = get_simple_loop_desc (loop); | |
563 | ||
564 | /* Check that loop is a candidate for a low-overhead looping insn. */ | |
565 | if (!doloop_valid_p (loop, desc)) | |
566 | { | |
567 | if (dump_file) | |
568 | fprintf (dump_file, | |
569 | "Doloop: The loop is not suitable.\n"); | |
570 | return false; | |
571 | } | |
572 | mode = desc->mode; | |
573 | ||
574 | est_niter = 3; | |
575 | if (desc->const_iter) | |
576 | est_niter = desc->niter; | |
577 | /* If the estimate on number of iterations is reliable (comes from profile | |
578 | feedback), use it. Do not use it normally, since the expected number | |
579 | of iterations of an unrolled loop is 2. */ | |
580 | if (loop->header->count) | |
581 | est_niter = expected_loop_iterations (loop); | |
582 | ||
583 | if (est_niter < 3) | |
584 | { | |
585 | if (dump_file) | |
586 | fprintf (dump_file, | |
587 | "Doloop: Too few iterations (%u) to be profitable.\n", | |
588 | est_niter); | |
589 | return false; | |
590 | } | |
591 | ||
45b9a14b BS |
592 | max_cost |
593 | = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST)); | |
594 | if (rtx_cost (desc->niter_expr, SET) > max_cost) | |
595 | { | |
596 | if (dump_file) | |
597 | fprintf (dump_file, | |
405f0587 | 598 | "Doloop: number of iterations too costly to compute.\n"); |
45b9a14b BS |
599 | return false; |
600 | } | |
601 | ||
a82bbcbb | 602 | count = copy_rtx (desc->niter_expr); |
689ba89d ZD |
603 | iterations = desc->const_iter ? desc->niter_expr : const0_rtx; |
604 | iterations_max = GEN_INT (desc->niter_max); | |
605 | level = get_loop_level (loop) + 1; | |
606 | ||
607 | /* Generate looping insn. If the pattern FAILs then give up trying | |
608 | to modify the loop since there is some aspect the back-end does | |
609 | not like. */ | |
610 | start_label = block_label (desc->in_edge->dest); | |
611 | doloop_reg = gen_reg_rtx (mode); | |
612 | doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, | |
613 | GEN_INT (level), start_label); | |
a82bbcbb ZD |
614 | |
615 | word_mode_size = GET_MODE_BITSIZE (word_mode); | |
616 | word_mode_max | |
617 | = ((unsigned HOST_WIDE_INT) 1 << (word_mode_size - 1) << 1) - 1; | |
618 | if (! doloop_seq | |
619 | && mode != word_mode | |
620 | /* Before trying mode different from the one in that # of iterations is | |
621 | computed, we must be sure that the number of iterations fits into | |
622 | the new mode. */ | |
623 | && (word_mode_size >= GET_MODE_BITSIZE (mode) | |
624 | || desc->niter_max <= word_mode_max)) | |
689ba89d | 625 | { |
a82bbcbb ZD |
626 | if (word_mode_size > GET_MODE_BITSIZE (mode)) |
627 | { | |
628 | count = simplify_gen_unary (ZERO_EXTEND, word_mode, | |
a252f3e8 | 629 | count, mode); |
a82bbcbb ZD |
630 | iterations = simplify_gen_unary (ZERO_EXTEND, word_mode, |
631 | iterations, mode); | |
632 | iterations_max = simplify_gen_unary (ZERO_EXTEND, word_mode, | |
633 | iterations_max, mode); | |
634 | } | |
635 | else | |
636 | { | |
637 | count = lowpart_subreg (word_mode, count, mode); | |
638 | iterations = lowpart_subreg (word_mode, iterations, mode); | |
639 | iterations_max = lowpart_subreg (word_mode, iterations_max, mode); | |
640 | } | |
689ba89d ZD |
641 | PUT_MODE (doloop_reg, word_mode); |
642 | doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, | |
643 | GEN_INT (level), start_label); | |
644 | } | |
645 | if (! doloop_seq) | |
646 | { | |
647 | if (dump_file) | |
648 | fprintf (dump_file, | |
649 | "Doloop: Target unwilling to use doloop pattern!\n"); | |
650 | return false; | |
651 | } | |
652 | ||
653 | /* If multiple instructions were created, the last must be the | |
654 | jump instruction. Also, a raw define_insn may yield a plain | |
655 | pattern. */ | |
656 | doloop_pat = doloop_seq; | |
657 | if (INSN_P (doloop_pat)) | |
658 | { | |
659 | while (NEXT_INSN (doloop_pat) != NULL_RTX) | |
660 | doloop_pat = NEXT_INSN (doloop_pat); | |
46dc0789 | 661 | if (!JUMP_P (doloop_pat)) |
689ba89d ZD |
662 | doloop_pat = NULL_RTX; |
663 | } | |
664 | ||
665 | if (! doloop_pat | |
666 | || ! (condition = doloop_condition_get (doloop_pat))) | |
667 | { | |
668 | if (dump_file) | |
669 | fprintf (dump_file, "Doloop: Unrecognizable doloop pattern!\n"); | |
670 | return false; | |
671 | } | |
672 | ||
a82bbcbb | 673 | doloop_modify (loop, desc, doloop_seq, condition, count); |
689ba89d ZD |
674 | return true; |
675 | } | |
676 | ||
d73be268 | 677 | /* This is the main entry point. Process all loops using doloop_optimize. */ |
689ba89d ZD |
678 | |
679 | void | |
d73be268 | 680 | doloop_optimize_loops (void) |
689ba89d | 681 | { |
42fd6772 | 682 | loop_iterator li; |
689ba89d ZD |
683 | struct loop *loop; |
684 | ||
42fd6772 | 685 | FOR_EACH_LOOP (li, loop, 0) |
689ba89d | 686 | { |
689ba89d ZD |
687 | doloop_optimize (loop); |
688 | } | |
689 | ||
690 | iv_analysis_done (); | |
691 | ||
692 | #ifdef ENABLE_CHECKING | |
693 | verify_dominators (CDI_DOMINATORS); | |
d73be268 | 694 | verify_loop_structure (); |
689ba89d ZD |
695 | #endif |
696 | } | |
697 | #endif /* HAVE_doloop_end */ | |
698 |